Ratio adjustable channel hopping enhancement for heterogeneous cognitive radio networks

In a cognitive radio network (CRN), a premise for two nodes to communicate is having a rendezvous which means that they switch to the same channel simultaneously. Most existing channel hopping solutions for the rendezvous problem is for a homogeneous CRN where nodes have the same type of cognitive radio and thus can sense the same spectrum. In reality, nodes have different types of cognitive radios and hence the spectrums being sensed are different. In such a heterogeneous CRN, designing a channel hopping mechanism to provide rendezvous guarantee is challenging. Besides, while determining the channel hopping sequences, existing channel hopping protocols enable nodes to switch to different channels with predefined channel hopping sequences. Such mechanisms are suboptimal since they do not consider different channel conditions. In this paper, we propose a ratio adjustable channel hopping protocol (RACH) for heterogeneous CRNs. RACH provides rendezvous guarantee between any pair of nodes and enables a node to dynamically adjust the ratio of each channel being used. Nodes running RACH use three consecutive odd numbers to determine the schedule for a particular channel. Utilizing the property that two different sets of three consecutive odd numbers are relatively primes, RACH provides rendezvous guarantee for two nodes on each channel. RACH allows nodes to change the set of consecutive odd numbers to adjust the ratio of a channel being switched to. Such a mechanism enables a node to tune to a better channel more frequently to enhance its rendezvous probability to other nodes. Simulation results verify that RACH improves network performance in terms of time to rendezvous and throughput when compared with an existing channel hopping protocol for heterogeneous CRNs.